SAW transducer devices, by way of example, have important uses in communications (e.g. cellular radio, data transmission, etc.) radar, signal processing systems, and so on. SAW transducer devices have proven attractive because they are inexpensive, of compact size, and are amenable to specific design criteria; e.g., phase and amplitude can be controlled or designed independently.
Conventional SAW transducers consist of three wave velocity regions: free-surface (crystal surface) semi-metal surface (interdigital electrodes) and metal surface (bus bars). The electrodes and bus bars, in effect, form an acoustic waveguide since both the metal bus bars and electrodes provide a "slow wave" structure.
Unfortunately, large portions of the acoustic energy are directed along the bus bars of the transducers. This leakage of energy to the bus bars leads to distortion and reflection of waves and increases the device insertion loss.
Accordingly, in order to minimize distortion, reflection, and insertion loss, the acoustic energy should be confined to the interdigital electrode region.